Effect of electron correlation on high harmonic generation of helium atoms in intense laser fields

Xiaoxu Guan( Department of Chemistry, University of Kansas)

Xiao-Min Tong( University of Tsukuba, Japan)

Shih-I Chu( Department of Chemistry, University of Kansas)

We present a time-dependent generalized pseudospectral (TDGPS)
approach in {\em hyperspherical coordinates} for fully {\em ab
initio} nonperturbative and high-precision treatment of
multiphoton electron-correlated dynamics of atomic systems in
intense laser fields [1]. The procedure is applied to the
investigation of high-order-harmonic generation (HHG) of
helium atoms in ultrashort laser pulses at a KrF wavelength of
248.6 nm. The 6D coupled hyperspherical-adiabatic-channel
equations are discretized and solved
efficiently and accurately by means of the TDGPS method. The
effects of electron correlation and doubly excited states on
HHG are explored in detail. A HHG peak with Fano line profile
is identified which can be attributed to a broad
resonance of doubly excited states. Comparison of the HHG
spectra of the {\em ab initio} two-electron and the single-
active-electron model calculations is also presented.
\vspace{1mm}
\noindent
[1] X. Guan, X.-M. Tong, and S. I. Chu, Phys. Rev. A (in
press).

This work was supported by the
Chemical Sciences, Geosciences and Biosciences Division,
Office of Basic Energy Sciences,
Office of Science, U.S. Department of Energy.